DH loves the summer and would go all the time. He loves the heat. Crowd-wide, IMO, the last bit of September. Weather-wise I have always enjoyed the 3rd week in October. I don't like to be gone over a holiday so October into November is out. We've gone a few times, just this past November, on November 1 and have been plagued by either bad weather (flying out) or terrible DVC studio availability. I also enjoy the 2nd week of December but it is chilly (which I like and DH does not). The week before Thanksgiving is pretty good weather and crowds but it needs to be booked early.
Our sweet spot is mid-October - warm enough for DH and cool enough for me. We're no longer big on F&W but I do enjoy the WS in the evening. In October the WS lights don't come on until 8:30p.